Superabsorbent refers to a water-swellable, water-insoluble, organic or inorganic material capable of absorbing at least about 10 times its weight and up to about 30 times its weight in an aqueous solution containing 0.9 weight percent sodium chloride solution in water. A superabsorbent polymer is a crosslinked neutralized polymer which is capable of absorbing large amounts of aqueous liquids and body fluids, such as urine or blood, with swelling and the formation of hydrogels, and of retaining them under a certain pressure in accordance with the general definition of superabsorbent.
The superabsorbent polymers that are currently commercially available include crosslinked polyacrylic acids or crosslinked starch-acrylic acid graft polymers, in which some of the carboxyl groups are neutralized with sodium hydroxide solution or potassium hydroxide solution. As a result of these absorbent properties, these polymers are chiefly used for incorporation into sanitary articles, such as babies' diapers, incontinence products or sanitary towels.
For fit, comfort and aesthetic reasons and from environmental aspects, there is an increasing trend to make sanitary articles smaller and thinner. This is being accomplished by reducing the content of the high volume fluff fiber of these articles. To ensure a constant total retention capacity of body fluids in the sanitary articles, more superabsorbent polymer content is being used in these sanitary articles. As a result of this, superabsorbent polymers must have increased permeability characteristics while retaining other characteristics such as adequate absorption and retention.
To obtain a superabsorbent polymer with high gel strength, the degree of crosslinking of the polymer may be increased, which necessarily results in a reduction in the swellability and the retention capacity. To achieve the increased permeabilities needed in extremely thin, next generation articles with low fiber content, current art has taught to increase the amount of covalent crosslinking to such high levels that the absorption and retention values of the superabsorbent polymers are reduced to undesirably low levels.
Aminopolysaccaride polymers include chitosan, a deacetylated chitin, is a cation-active, poly-primary amine with diverse applications in fields such as dispersing agents, adhesives, pesticides, wastewater treatment, food processing, and wound healing. Unfortunately, the known modified chitosan materials generally do not possess absorptive properties comparable to many of the synthetic, highly absorptive materials. This has prevented widespread use of such chitosan materials in absorbent personal care products.
It is therefore an object of the present invention to provide an absorbing polymer composition that exhibits excellent properties such as capabilities of maintaining high liquid permeability, hydrophilicity and liquid retention even when the superabsorbent polymer is increased in percent by weight based on the absorbent structure.